Polyurethane foams with a wide variety of physical properties have long been manufactured on a commercial scale by the known isocyanate polyaddition process from compounds containing several active hydrogen atoms, in particular compounds containing hydroxyl and/or carboxyl groups, and polyisocyanates with the addition of water and/or blowing agents and optionally catalysts, emulsifiers and other additives (Angew. Chem. A. 59 (1947), page 257). Given a suitable choice of components, either flexible or rigid foams or any products between these extremes may be obtained.
Polyurethane foams are preferably produced from liquid starting components, either by mixing all the starting materials together in a one-shot process or by first preparing a prepolymer containing isocyanate groups from a polyol and an excess of polyisocyanate and then foaming this prepolymer, e.g., with reaction with water.
Tertiary amines have become well established as catalysts in the production of polyurethane foams. They accelerate the reaction of hydroxyl and carboxyl groups with isocyanate groups (urethane reaction) and the reaction between water and isocyanates (blowing reaction). The velocities of the two reactions which take place simultaneously in the one-shot process have to be adjusted relative to each other. Cross-linking reactions which give rise to the formation of allophanate, biuret and cyanurate structures take place during the foaming process in addition to the reactions mentioned above.
In view of the large number of reactions taking place, the catalyst must be chosen so that it insures synchronous adjustment of the reactions to each other. At the same time, the catalyst must not be fixed too early in the process by incorporation in the foam, nor must it subsequently accelerate hydrolytic degradation of the foam product. This problem has not up to now been completely solved.
There are a number of known catalysts for the production of polyurethane plastics. Tertiary amines suitable as cross-linking catalysts are described for example in U.S. Pat. Nos. 3,036,020 and 3,239,480. Additionally, tertiary amines may be used as blowing catalysts. Examples of such amines include those described in U.S. Pat. No. 4,143,003, and U.S. application Ser. No. 920,563 filed June 29, 1978. However, these catalysts by themselves have not completely answered all of the problems associated with polyurethane plastic production. German Offenlegungsschrift No. 2,624,528 indicates that catalysts of the general formula: ##STR4## may be combined with N,N,N',N'-tetramethyl ethylene diamine, pentamethyl diethylene triamine or N,N,N',N'-tetramethyl-1,3-butane diamine.
It has surprisingly been found that the property spectrum of polyurethane plastics can be adjusted with the catalyst combination used in accordance with the present invention in such a way that:
1. A very short in-mold time, PA1 2. Minimal brittleness, PA1 3. Good adhesion to surface layers, such as phosphatized and lacquered sheet metal, melamine resins, ABS and, in particular, polystyrene, PA1 4. Substantial freedom from odor, PA1 5. Outstanding fluidity, PA1 6. A low gross density PA1 R' and R" represent hydrogen or the same or different C.sub.1 -C.sub.3 -alkyl radicals, preferably CH.sub.3 -- or C.sub.2 H.sub.5 -- radicals, and PA1 n represents an integer of from 1 to 10, preferably from 4 to 8, PA1 X represents oxygen or ##STR7## wherein R'" represents a C.sub.1 -C.sub.5 alkyl radical, preferably a CH.sub.3 -- or C.sub.2 H.sub.5 -- radical, PA1 p represents an integer of from 2 to 4 and PA1 r represents an integer of from 1 to 3, and PA1 m and o which may be the same or different, represent numbers ranging from 1 to 10, preferably from 1 to 3 in value. PA1 n=2-4, preferably 2, and PA1 Q represents an aliphatic hydrocarbon radical containing from 2 to 18 carbon atoms, preferably from 6 to 10 carbon atoms, a cycloaliphatic hydrocarbon radical containing from 4 to 15, preferably from 5 to 10 carbon atoms, an aromatic hydrocarbon radical containing from 6 to 15 carbon atoms, preferably from 6 to 13 carbon atoms, or an araliphatic hydrocarbon radical containing from 8 to 15 carbon atoms, preferably from 8 to 13 carbon atoms. Specific examples of these types of compounds are: ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and 1,4-diisocyanate and mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl cyclohexane (German Auslegeschrift No. 1,202,785 and U.S. Pat. No. 3,401,190), 2,4- and 2,6-hexahydrotolylene diisocyanate and mixtures of these isomers, hexahydro-1,3- and/or -1,4-phenylene diisocyanate, perhydro-2,4'- and/or -4,4'-diphenyl methane diisocyanate, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanate and mixtures of these isomers, diphenyl methane-2,4'- and/or -4,4'-diisocyanate, and naphthalene-1,5-diisocyanate. PA1 R represents an alkylene radical containing from 1 to 10, preferably from 2 to 6 carbon atoms or a cycloalkylene or arylene radical containing from 6 to 10 carbon atoms, PA1 x=2 to 6 and PA1 y=3 to 5, PA1 R' represents an alkylene radical containing from 2 to 15 carbon atoms, preferably from 2 to 6 carbon atoms or a cycloalkylene or arylene radical containing from 6 to 15 carbon atoms, and PA1 x represents a number of from 2 to 6, for example 1,6-hexamethylene-bis-(.beta.-hydroxyethyl urethane) or 4,4'-diphenyl methane-bis-(.delta.-hydroxybutyl urethane) and diol ureas corresponding to the following general formula: ##STR8## wherein R" represents an alkylene radical containing from 2 to 15 carbon atoms preferably from 2 to 9 carbon atoms or a cycloalkylene or arylene radical containing from 6 to 15 carbon atoms, PA1 R'" represents hydrogen or a methyl group and PA1 x represents the number 2 or 3,
can be simultaneously obtained.